This application claims the priority of the commonly owned copending German patent application Serial No. 100 62 499.5 filed Dec. 14, 2000. The disclosure of the said commonly owned copending German patent application, as well as that of each U.S. and foreign patent and patent application identified in the specification of the present application, is incorporated herein by reference.
The invention relates to improvements in torque transmitting apparatus, and more particularly to improvements in hydraulic torque converters which can be utilized with advantage in the power trains of motor vehicles, e.g., between the rotary output element of the prime mover (such as an internal combustion engine) and the input element (such as a shaft) of a change-speed transmission.
A conventional hydrokinetic torque converter in the power train of a motor vehicle normally comprises a housing which shares the angular movements of the output element (such as the crankshaft) of the engine, a pump which shares the angular movements of the housing, a turbine which can receive torque from the housing by way of a body of hydraulic fluid confined in the housing and being circulated by the vanes or blades of the pump, as well as an output member (e.g., a hub) which can receive torque from the turbine to transmit torque to a driven member such as the input shaft of the change-speed transmission. The torque converter can further comprise a bypass clutch or lockup clutch (hereinafter called bypass clutch) which, when necessary or desired, transmits torque directly between the pump or housing and the turbine. Still further, such conventional torque converter can also comprise at least one torsional vibration damper which operates in the power train between the housing and the output member.
In many conventional torque converters of the above outlined character, a portion of the bypass clutch is fixedly secured to the input of the torsional vibration damper. Reference may be had, for example, to published German patent application Serial No. 199 63 236 A1. The piston of the bypass clutch is or can be riveted to the input of the torsional vibration damper and such input comprises two annular flanges. During actuation (engagement or disengagement) of the bypass clutch, the piston of the bypass clutch is caused to move axially and to thus frictionally engage or become disengaged from the housing of the torque converter. Such axial movement of the piston entails a movement of the output of the torsional vibration damper because the output is provided with gear teeth mating with complementary gear teeth on the hub of the torque converter.
It can happen that the mating gear teeth generate pronounced friction or that they jam. In fact, the tension between the input of the torsional vibration damper and the piston of the bypass clutch, and/or non-uniform engagement of the piston of the bypass clutch with the friction surface of the housing of the torque converter, can cause the development of excessive stresses, a cracking of cooperating parts and fatigue-induced breaks. Such undesirable phenomena are particularly likely to develop in the parts which are riveted to each other. Still further, excessive tension between the piston of the bypass clutch and the input of the torsional vibration damper is likely to develop when the piston is caused to frictionally engage the housing with attendant deformation (particularly in the axial direction of the bypass clutch) when the pressure of hydraulic fluid in the cylinder chamber for the piston increases, i.e., when the piston is called upon to transmit torque from the housing to the output of the torque converter by establishing a direct power transmitting path from the output element of the prime mover, through the housing of the torque converter and to the output of the latter, i.e., by bypassing the pump and the turbine of the torque converter.
The torsional vibration damper comprises coil springs or other suitable resilient elements which act in the circumferential direction of the input and output when the input turns relative to the output and/or vice versa. When the RPM of the torsional vibration damper is very high, the springs are held against radially outward movement under the action of centrifugal force. The means for preventing such radially outward movements of the springs are costly as well as bulky because they take up room as considered axially as well as radially of the damper. In order to achieve most satisfactory friction within the entire RPM range of the springs, it is necessary to establish an optimum relationship between the parts which can or should turn relative to each other, especially between the coil springs on the one hand and the input and/or output of the torsional vibration damper on the other hand.
It is often advisable to connect the torque converter to an axially elastic disc or wall which is attached to and receives torque from the output shaft of the prime mover (such as the crankshaft of the engine) in the power plant of a motor vehicle. The connection is normally established by resorting to threaded fasteners having shanks mating with internal threads provided in one of the torque converter and the disc. This normally involves individual application and tightening of each of a plurality of threaded fasteners. Such tightening is carried out by resorting to a suitable tool which can reach the fasteners through one or more access openings provided in the housing or bell of the change-speed transmission of the power train. The torque converter must be caused to turn, at least at intervals, in order to afford access to the fasteners. Such modes of affixing the torque converter to the torsional vibration damper and of mounting the damper in the torque converter are time-consuming and necessitate the hiring of highly skilled artisans. The situation is complicated because the installation of a torque converter in the power train of a vehicle also invariably necessitates the hiring of highly skilled artisans who are capable of carrying out the above outlined undertakings in addition to centering of cooperating moving (rotary) parts relative to the adjacent part or parts.
An object of the instant invention is to provide a hydraulic torque converter which is more reliable than heretofore known torque converters and whose useful life is much longer than those of the aforediscussed and other conventional apparatus of such character.
Another object of the invention is to provide a torque converter which can be assembled and installed in the power train of a motor vehicle or the like in a manner much simpler than conventional torque converters.
A further object of the present invention is to provide a torque converter which is constructed and assembled with a view to reduce the effects of fatigue upon its useful life and/or upon the reliability of its operation and which is more likely to withstand the effects of unanticipated stresses, hard-to-detect cracks and/or breaks as well as weakening of joints, connections and wear-induced problems than conventional torque converters.
An additional object of this invention is to provide a novel and improved method of assembling a torque converter and of installing such apparatusxe2x80x94in partly or fully assembled conditionxe2x80x94in the power train of a motor vehicle.
Still another object of the invention is to provide one or more novel and improved torsional vibration dampers for use in the aforediscussed novel hydraulic torque converter.
A further object of the invention is to provide a novel and improved combination of a bypass clutch and one or more torsional vibration dampers for use in a hydraulic torque converter.
Another object of this invention is to provide a torque converter which embodies a bypass clutch and wherein the generation and/or application or utilization of friction and/or damping can be initiated and controlled in a manner more reliable and more predictable than in conventional torque converters.
An additional object of the invention is to provide a torque converter whose operation is more reliable and more predictable within the entire RPM range of the rotary output element or elements of the prime mover, such as the camshaft or the crankshaft of the internal combustion engine in the power train of a motor vehicle, than the operation of conventional torque converters.
Still another object of the invention is to provide a novel and improved method of operatively connecting the improved torque converter with a shaft, disc or another rotary output element of a prime mover.
A further object of our invention is to provide a torque converter wherein one or more rotary and/or otherwise movable parts of the bypass clutch, of one or more torsional vibration dampers and/or one or more other components can be centered in a manner simpler, more reliable and less time-consuming than that required for analogous manipulation(s) of components in conventional torque converters.
Another object of the invention is to simplify the assembly of the torque converter with a prime mover and/or with a driven unit (such as a variable-speed transmission) in the power train of a motor vehicle.
An additional object of the invention is to provide a torque converter which is constructed and assembled in such a way that its space requirements in a motor vehicle (such as between the engine and the transmission) are much less than in heretofore known power trains.
Still another object of the invention is to provide a power train which can be utilized in any one of a large number of different power trains to meet one or more specific or broad requirements pertaining to savings in space, material and/or number of parts, to reliability and/or useful life, to the possibility to occupy space which is avaiable under the hood of or elsewhere in a motor vehicle and/or to meet two or more of the above-enumerated and/or other prerequisites.
A further object of the instant invention is to provide a power train, particularly for use in a motor vehicle, which embodies a torque converter exhibiting at least some of the above-enumerated features and attributes.
One feature of the present invention resides in the provision of a hydraulic torque converter which comprises a housing arranged to rotate about a predetermined axis, to confine a supply of a suitable hydraulic fluid and to receive torque from an output element of a prime mover (e.g., from the crankshaft of an internal combustion engine in the power train of a motor vehicle). The improved torque converter further comprises a pump which is disposed in and is arranged to rotate with the housing about the predetermined axis, and an annular turbine which is coaxial with the pump, which is disposed in the housing and which is arranged to receive torque from the fluid in the housing in response to rotation of the pump. The improved torque converter also comprises a rotary input element (e.g., the input shaft of a change-speed transmission) which is coaxial with the housing, a rotary output member (such as a hub) which is arranged to transmit torque between the input element and at least one of the pump, turbine and housing, a bypass clutch which is engageable to transmit force between the pump and the turbine during predetermined stages of operation of the torque converter, and at least one torsional vibration damper in a power flow between the housing and the output member. The damper comprises an input, an output which is coaxial with the housing and with the input and is rotatable relative to the input, and energy storing means arranged to oppose rotation of the input and the output relative to each other.
The improved torque converter can further comprise a stator which, if used, is installed between the pump and the turbine.
The input element can include or constitute or form part of a shaft of an automatic change-speed transmission.
The bypass clutch can include a substantially disc-shaped member and the torque converter can further comprise means for resiliently connecting the disc-shaped member to the input of the damper with freedom of movement in the direction of the axis of the housing. The substantially disc-shaped member can include or constitute a piston of the bypass clutch, and such torque converter can further comprise a force-locking connection between the piston and the housing; such connection can include friction surfaces which contact each other in the engaged condition of the bypass clutch.
The aforementioned member (piston) of the bypass clutch can be connected with the input or with the output of the damper at a plurality of points which are spaced apart from each other in the circumferential direction of the turbine. The input or the output of the damper and/or the member (piston) of the bypass clutch can be provided with stiffness reducing means disposed at least partially radially inwardly of the aforementioned array of connection points, namely with means for reducing the stiffness of the input, output or piston in the direction of the predetermined axis.
The stiffness reducing means can include an annular array of recesses in the input, output or piston, and each such recess can be adjacent one of the aforementioned plurality of points. For example, each recess can include an arcuate slit which partially surrounds one of the points. The width of one end portion of each slit can exceed the width of the other end portion and/or the width of an intermediate portion of the respective slit. One end portion of each recess or slit in the input, output or piston can extend radially outwardly beyond at least one of the aforementioned points.
If the recesses are slits provided in the input of the torsional vibration damper, such slits can be provided in the radially outermost portion of the input and can have open ends at the periphery of the input.
An enlarged end of each slit can be spaced apart from the axis of the housing the same distance as the aforementioned points.
The slits, recesses or other suitable stiffness reducing means can be provided in the input or output of the damper and/or in the piston of the bypass clutch during a first stage of assembly of the damper with the housing and the output member, and the input can undergo a shaping treatment (such as the imparting of the final shape) during a second stage which follows the first stage of assembly of the damper with the housing and with the output member.
The damper can be installed in a power flow between the bypass clutch and the output member or in a power flow between the turbine and the output member.
The input of the damper can include at least two walls or panels, and such torque converter can further comprise means (such as rivets) for connecting at least one wall of the input with a member (such as a piston) of the bypass clutch.
A portion of the bypass clutch can be placed next to a portion of the torsional vibration damper, and such torque converter can further comprise an annular array of fasteners (such as rivets) which spacedly surround the axis of the housing and connect the two portions to each other. Such torque converter can further comprise means (such as the aforementioned slots) for reducing the stiffness of at least one of the interconnected portions in the axial direction of the housing. The slots, recesses or analogous stiffness reducing means are or can be adjacent the fasteners. Each such recess or slot can be open as seen radially outwardly away from the axis of the housing and closed radially inwardly of neighboring fasteners. The recesses can alternate with the fasteners, and the widths of at least some of the recessesxe2x80x94as seen in the circumferential direction of the portions of the damper and bypass clutchxe2x80x94can increase in a direction toward the axis of the housing.
It is also possible to provide the input or the output of the damper and/or the piston of the bypass clutch with recesses having closed radially inner end portions nearest to the axis of the housing and bounded by at least substantially circular surfaces of the input, output and/or piston; each such recess can resemble a keyhole.
The widths of at least some of the recessesxe2x80x94as seen in the circumferential direction of the housingxe2x80x94can decrease in a direction toward the axis of the housing. For example, such recesses can be bounded by an undulate peripheral surface of the input, output and/or piston.
A portion (such as the aforementioned piston) of the bypass clutch can be connected to a portion (such as the input) of the damper by suitable springs with limited freedom of movement in the direction of the axis of the housing of the improved torque converter. The springs can include an annuar array of leaf springs which spacedly surround the axis of the housing. Such torque converter can further comprise means for non-rotatably connecting the input of the damper with the turbine. The piston of the bypass clutch and the housing include annular portions which frictionally engage each other in the engaged condition of the bypass clutch, and the aforementioned leaf springs can connect the input of the damper with a radially outermost part of the aforementioned portion (piston) of the bypass clutch.
The energy storing means of the at least one damper can include an annulus of coil springs and means for limiting the movability of such springs at least radially of the axis of the housing. The means for limiting can include a ring which is surrounded by the convolutions of the coil springs with limited freedom of movement of the springs and ring relative to each other radially of the axis of the housing. Such torque converter can further comprise means for connecting the ring to the damper, namely to the input or the output of the damper. The ring can be made of any suitable material, especially a metallic or a plastic material.
The means for limiting can include a preshaped annular member and the convolutions of the coil springs forming part of the damper spacedly surround the preshaped annular member. The end portions of the latter can be affixed to each other by bonding (such as welding), by hooking (i.e., by resorting to one or more hooks at one end of the annular member and to one or more eyelets for such hook or hooks at the other end of the annular member) or by nesting (e.g., by fitting a male member at one end into a complementary female member at the other end of the annular member).
The input and/or the output of the damper can include means for locating the annular member relative to the input and the output in at least one of the directions including radially of the axis of the housing and in the direction of such axis. The locating means can include an annular array of discrete projections provided on the input and/or on the output of the damper. The projections can further serve as a means for tensioning the annular member. Each such projection can include a deformed portion of the input and/or the output of the damper.
The ratio of the diameter d of the wire of the ring to the inner diameters D of convolutions of the coil springs is or can be determined by the relationship 0.8*D greater than d greater than 0.2*D, preferably by the relationship 0.6*D greater than d greater than 0.3*D.
The springs of the energy storing means can be received in recesses provided therefor in the input of the damper, and such input can be further provided with at least substantially radial arms alternating with the recesses, as seen in the circumferential direction of the damper. The output of such damper can include entraining portions which cooperate with the arms to stress the springs in response to rotation of the input relative to the output and/or vice versa.
The arms and/or the entraining means can be provided with surfaces which at least substantially conform to the surfaces of adjacent portions of the springs forming part of the energy storing means.
One or more springs of the energy storing means can be installed in prestressed condition, i.e., such springs are caused by the adjacent arms to store energy even in neutral angular positions of the input and output of the damper relative to each other. Alternatively or in addition to the just mentioned feature, the springs can be maintained in prestressed condition by the entraining portion of the output of the damper. The recesses of the input of the damper can be bounded by surfaces making right angles with each other.
Another feature of the present invention resides in the provision of a hydraulic torque converter which comprises a housing including a mass and being arranged to rotate about a predetermined axis, to confine a supply of hydraulic fluid and to receive torque from an output element of a prime mover. The improved torque converter further comprises a pump which is disposed in and is arranged to rotate with the housing about the latter""s axis, an annular turbine which is coaxial with the pump, which is disposed in the housing and which is arranged to receive torque from the fluid in the housing in response to rotation of the pump, a rotary input element which is coaxial with the housing, a rotary output member which is arranged to transmit torque between the input element and the pump, housing and/or turbine, and a bypass clutch which is engageable to transmit force between the pump and the turbine during predetermined stages of operation of the torque converter. The latter further comprises at least one torsional vibration damper including an input, an output coaxial with the housing and with the input and rotatable relative to the input, energy storing means arranged to oppose rotation of the input and output relative to each other, and a torque transmitting member between the output element and the input. Still further, the torque converter comprises an annular array of retaining members provided on the mass and received in openings provided therefor in the torque transmitting member, and means for holding the retaining members in the respective openings.
The retaining members can include pins having axes at least substantially parallel to the axis of the housing and including end portions which extend or can extend through and beyond the respective openings; the holding means can engage such end portions of the pins. Such holding means can extend at least substantially circumferentially of the torque transmitting member.
In accordance with one presently preferred embodiment, the holding means includes a ring-shaped support and discrete holding members provided on the ring-shaped support and each engaging one of the retaining members.
The torque transmitting member can be disposed between the prime mover and the mass of the housing, as seen in the axial direction of the housing.
At least one of the retaining members can have an at least substantially conical shape and the corresponding opening has a complementary shape to snugly receive the conical retaining member.
The openings are or can be provided in a reinforced portion of the torque transmitting member; the latter can include a substantially disc-shaped body having a folded over radially outermost part which constitutes the reinforced portion of the torque transmitting member.
The mass of the housing can constitute an annular body, and the holding means can include forks each of which has prongs extending at least substantially circumferentially of the annular mass and engaging free end portions of the respective retaining members. The prongs can be received in grooves provided therefor in the free end portions of the respective retaining members. It is advisable to ensure that the forks are maintained in frictional engagement with the torque transmitting member and with the respective retaining members.
As already mentioned hereinbefore, the holding means can include a discrete holding member for each of the retaining members and a ring-shaped support for the holding members. Such torque converter can further comprise means for securing the ring-shaped support to the torque transmitting member against accidental separation from the latter.
The retaining members can include or constitute forks which extend circumferentially of the ring-shaped support. Each fork engages one of the retaining members and is separable from the respective retaining member in response to rotation of the ring-shaped support relative to the mass and/or vice versa. The forks cooperate with the retaining members to hold the ring-shaped support against movement relative to the mass in the axial direction of the housing.
The torque converter can further comprise means for preventing undesired rotation of the ring-shaped support relative to the mass when the retaining members are held in the respective openings. The rotation preventing means can comprise at least one snap fastener; such snap fastener can include a detent which is provided on the holder or on the torque transmitting member of the damper and an opening for the detent in the torque transmitting member or in the holder.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved torque converter itself, however, both as to its construction and the modes of assembling, installing and utilizing the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the acccompanying drawings.